/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.method;

import java.lang.annotation.Annotation;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Set;

import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.BeanFactoryUtils;
import org.springframework.context.ApplicationContext;
import org.springframework.core.Ordered;
import org.springframework.core.annotation.AnnotatedElementUtils;
import org.springframework.core.annotation.AnnotationUtils;
import org.springframework.core.annotation.OrderUtils;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;
import org.springframework.util.StringUtils;
import org.springframework.web.bind.annotation.ControllerAdvice;

/**
 * Encapsulates information about an {@linkplain ControllerAdvice @ControllerAdvice}
 * Spring-managed bean without necessarily requiring it to be instantiated.
 *
 * <p>The {@link #findAnnotatedBeans(ApplicationContext)} method can be used to
 * discover such beans. However, a {@code ControllerAdviceBean} may be created
 * from any object, including ones without an {@code @ControllerAdvice}.
 *
 * @author Rossen Stoyanchev
 * @author Brian Clozel
 * @author Juergen Hoeller
 * @since 3.2
 */
public class ControllerAdviceBean implements Ordered {

    private final Object bean;

    @Nullable
    private final BeanFactory beanFactory;

    private final int order;

    private final Set<String> basePackages;

    private final List<Class<?>> assignableTypes;

    private final List<Class<? extends Annotation>> annotations;


    /**
     * Create a {@code ControllerAdviceBean} using the given bean instance.
     *
     * @param bean the bean instance
     */
    public ControllerAdviceBean(Object bean) {
        this(bean, null);
    }

    /**
     * Create a {@code ControllerAdviceBean} using the given bean name.
     *
     * @param beanName the name of the bean
     * @param beanFactory a BeanFactory that can be used later to resolve the bean
     */
    public ControllerAdviceBean(String beanName, @Nullable BeanFactory beanFactory) {
        this((Object) beanName, beanFactory);
    }

    private ControllerAdviceBean(Object bean, @Nullable BeanFactory beanFactory) {
        this.bean = bean;
        this.beanFactory = beanFactory;
        Class<?> beanType;

        if (bean instanceof String) {
            String beanName = (String) bean;
            Assert.hasText(beanName, "Bean name must not be null");
            Assert.notNull(beanFactory, "BeanFactory must not be null");
            if (!beanFactory.containsBean(beanName)) {
                throw new IllegalArgumentException("BeanFactory [" + beanFactory +
                        "] does not contain specified controller advice bean '" + beanName + "'");
            }
            beanType = this.beanFactory.getType(beanName);
            this.order = initOrderFromBeanType(beanType);
        } else {
            Assert.notNull(bean, "Bean must not be null");
            beanType = bean.getClass();
            this.order = initOrderFromBean(bean);
        }

        ControllerAdvice annotation = (beanType != null ?
                                       AnnotatedElementUtils.findMergedAnnotation(beanType, ControllerAdvice.class)
                                                        : null);

        if (annotation != null) {
            this.basePackages = initBasePackages(annotation);
            this.assignableTypes = Arrays.asList(annotation.assignableTypes());
            this.annotations = Arrays.asList(annotation.annotations());
        } else {
            this.basePackages = Collections.emptySet();
            this.assignableTypes = Collections.emptyList();
            this.annotations = Collections.emptyList();
        }
    }

    /**
     * Find the names of beans annotated with
     * {@linkplain ControllerAdvice @ControllerAdvice} in the given
     * ApplicationContext and wrap them as {@code ControllerAdviceBean} instances.
     */
    public static List<ControllerAdviceBean> findAnnotatedBeans(ApplicationContext applicationContext) {
        List<ControllerAdviceBean> beans = new ArrayList<>();
        for (String name : BeanFactoryUtils.beanNamesForTypeIncludingAncestors(applicationContext, Object.class)) {
            if (applicationContext.findAnnotationOnBean(name, ControllerAdvice.class) != null) {
                beans.add(new ControllerAdviceBean(name, applicationContext));
            }
        }
        return beans;
    }

    private static int initOrderFromBean(Object bean) {
        return (bean instanceof Ordered ? ((Ordered) bean).getOrder() : initOrderFromBeanType(bean.getClass()));
    }

    private static int initOrderFromBeanType(@Nullable Class<?> beanType) {
        Integer order = null;
        if (beanType != null) {
            order = OrderUtils.getOrder(beanType);
        }
        return (order != null ? order : Ordered.LOWEST_PRECEDENCE);
    }

    private static Set<String> initBasePackages(ControllerAdvice annotation) {
        Set<String> basePackages = new LinkedHashSet<>();
        for (String basePackage : annotation.basePackages()) {
            if (StringUtils.hasText(basePackage)) {
                basePackages.add(adaptBasePackage(basePackage));
            }
        }
        for (Class<?> markerClass : annotation.basePackageClasses()) {
            basePackages.add(adaptBasePackage(ClassUtils.getPackageName(markerClass)));
        }
        return basePackages;
    }

    private static String adaptBasePackage(String basePackage) {
        return (basePackage.endsWith(".") ? basePackage : basePackage + ".");
    }

    /**
     * Returns the order value extracted from the {@link ControllerAdvice}
     * annotation, or {@link Ordered#LOWEST_PRECEDENCE} otherwise.
     */
    @Override
    public int getOrder() {
        return this.order;
    }

    /**
     * Return the type of the contained bean.
     * <p>If the bean type is a CGLIB-generated class, the original
     * user-defined class is returned.
     */
    @Nullable
    public Class<?> getBeanType() {
        Class<?> beanType = (this.bean instanceof String ?
                             obtainBeanFactory().getType((String) this.bean) : this.bean.getClass());
        return (beanType != null ? ClassUtils.getUserClass(beanType) : null);
    }

    /**
     * Return a bean instance if necessary resolving the bean name through the BeanFactory.
     */
    public Object resolveBean() {
        return (this.bean instanceof String ? obtainBeanFactory().getBean((String) this.bean) : this.bean);
    }

    private BeanFactory obtainBeanFactory() {
        Assert.state(this.beanFactory != null, "No BeanFactory set");
        return this.beanFactory;
    }

    /**
     * Check whether the given bean type should be assisted by this
     * {@code @ControllerAdvice} instance.
     *
     * @param beanType the type of the bean to check
     * @see org.springframework.web.bind.annotation.ControllerAdvice
     * @since 4.0
     */
    public boolean isApplicableToBeanType(@Nullable Class<?> beanType) {
        if (!hasSelectors()) {
            return true;
        } else if (beanType != null) {
            for (String basePackage : this.basePackages) {
                if (beanType.getName().startsWith(basePackage)) {
                    return true;
                }
            }
            for (Class<?> clazz : this.assignableTypes) {
                if (ClassUtils.isAssignable(clazz, beanType)) {
                    return true;
                }
            }
            for (Class<? extends Annotation> annotationClass : this.annotations) {
                if (AnnotationUtils.findAnnotation(beanType, annotationClass) != null) {
                    return true;
                }
            }
        }
        return false;
    }

    private boolean hasSelectors() {
        return (!this.basePackages.isEmpty() || !this.assignableTypes.isEmpty() || !this.annotations.isEmpty());
    }

    @Override
    public boolean equals(Object other) {
        if (this == other) {
            return true;
        }
        if (!(other instanceof ControllerAdviceBean)) {
            return false;
        }
        ControllerAdviceBean otherAdvice = (ControllerAdviceBean) other;
        return (this.bean.equals(otherAdvice.bean) && this.beanFactory == otherAdvice.beanFactory);
    }

    @Override
    public int hashCode() {
        return this.bean.hashCode();
    }

    @Override
    public String toString() {
        return this.bean.toString();
    }

}
